Liquid crystal display and method for manufacturing the same

ABSTRACT

A liquid crystal display includes a display panel; and an optical film on a bottom surface of the display panel, the optical film including a polarizer; a support sheet on a bottom surface of the polarizer; and a prism sheet on a bottom surface of the support sheet, the prism sheet having a base sheet, a prism portion, and a stitch portion over the base sheet. The prism portion includes a plurality of peaks and has a space defined by a direct contact between the plurality of peaks of the prism portion and the bottom surface of the support sheet.

This application is a Divisional of U.S. patent application Ser. No.15/338,585, filed Oct. 31, 2016, which claims the benefit of KoreanPatent Application No. 10-2015-0152686, filed on Oct. 30, 2015, bothwhich are hereby incorporated herein by reference for all purposes as iffully set forth herein.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a liquid crystal display having anoptical film embedded therein, and more particularly, to a liquidcrystal display having a structure in which an optical film for theuniformity and light focusing of backlight provided by a backlight unithas been laminated on a lower polarizer and a method for manufacturingthe same.

Discussion of the Related Art

The use of liquid crystal displays has gradually broadened due tocharacteristics such as light weight, thin profile, and low powerconsumption. The liquid crystal display is used in portable computers,such as notebook PCs, office automation devices, audio/video devices,and indoor and outdoor advertising displays. A transmission-type liquidcrystal display, which is the most common type of liquid crystaldisplay, displays an image by modulating light incident from a backlightunit through control of an electric field applied to a liquid crystallayer.

The backlight unit may be categorized into a direct-type and anedge-type. The direct-type backlight unit has an arrangement in which aplurality of light sources is disposed under a liquid crystal displaypanel. The edge-type backlight unit has an arrangement in which a lightsource is disposed to face the side of a light guide plate and aplurality of optical films is disposed between a liquid crystal displaypanel and the light guide plate. In the edge-type backlight unit, thelight source radiates light to one side of the light guide plate, andthe light guide plate converts a line light source or a dot light sourceinto a surface light source. The edge-type backlight unit has anadvantage in that it can be implemented with a thinner profile than thedirect-type backlight unit.

A liquid crystal display including an edge-type backlight unit accordingto a technology of the related art will be described with reference toFIGS. 1 and 2. FIG. 1 is an exploded perspective view showing thestructure of the liquid crystal display including an edge-type backlightunit according to the related art. FIG. 2 is a cross-sectional viewshowing the structure of the liquid crystal display including anedge-type backlight unit according to the related art taken along lineI-I′ of FIG. 1.

As shown in to FIGS. 1 and 2, the liquid crystal display according tothe related art includes a liquid crystal display panel LCP and anedge-type backlight unit EBLU disposed under the liquid crystal displaypanel LCP. The liquid crystal display panel LCP has a liquid crystallayer LC formed between an upper glass substrate SU and a lower glasssubstrate SL, and may be implemented in any liquid crystal mode.

The edge-type backlight unit EBLU includes a light source LS, a lightguide plate LG, and an optical film OPT. The edge-type backlight unitEBLU converts light output by the light source LS into a uniform surfacelight source using the light guide plate LG and the optical films OPT.Then, the edge-type backlight unit EBLU provides the converted uniformsurface light source to the liquid crystal display panel LCP.Furthermore, a reflection plate REF for returning light that leaksthrough the bottom of the light guide plate LG to the light guide plateLG may be further provided under the light guide plate LG.

A cover bottom CB is disposed under the reflection plate REF. The coverbottom CB may have a bowl shape in which the edge-type backlight unitEBLU is received. Furthermore, the cover bottom CB includes a materialhaving high thermal conductivity and high stiffness so that heat fromthe light source LS can be smoothly discharged to the outside. Forexample, the cover bottom CB may be fabricated using a metal plate, suchas aluminum (Al), aluminum nitride (AlN), an electronic galvanized steelsheet (EGI), stainless steel (SUS), Galvalume (SGLC), an aluminizedsteel sheet (so-called ALCOSTA), or a tin plate steel sheet (SPTE).Furthermore, the metal plate may be coated with a high conductivitymaterial for accelerating thermal transfer.

A guide panel GP and the top case TC are disposed at the edge of theliquid crystal display panel LCP. The guide panel GP has a rectangularmold frame in which glass fiber is mixed in a synthetic resin, such aspolycarbonate. The guide panel GP surrounds the top edge and sides ofthe liquid crystal display panel LCP and surrounds the sides of theedge-type backlight unit EBLU. The guide panel GP supports the liquidcrystal display panel LCP and regularly maintains the interval betweenthe liquid crystal display panel LCP and the optical film OPT. The topcase TC is made of a metal material, such as a zinc plate steel sheet,and has a structure that surrounds the top and sides of the guide panelGP. The top case TC is fixed to at least one of the guide panel GP andthe cover bottom CB by a hook or screw.

A light-emitting device having high brightness with low power, such asan LED, may be used as the light source LS. The light source LS supplieslight to the light guide plate LG. In the edge-type backlight unit EBLU,the light source LS is located at the side of the liquid crystal displaypanel LCP. That is, the light source LS supplies light to a side of thelight guide plate LG in accordance with at least one side of the lightguide plate LG.

The light guide plate LG has a panel-type rectangular parallelepipedshape having a face corresponding to the area of the liquid crystaldisplay panel LCP. The top surface of the light guide plate LG faces theliquid crystal display panel LCP. The light guide plate LG functions toreceive light from the light source LS installed on the side of thelight guide plate LG, to diffuse, and to distribute the light therein sothat the light is uniformly distributed within the light guide plate LG.Additionally, the light guide plate LG guides the light to the topsurface in which the liquid crystal display panel LCP has been disposed.

The light guided to the liquid crystal display panel LCP by the lightguide plate LG is not suitable for being used as backlight. For example,the light may not have a uniform brightness distribution over the entirearea of the liquid crystal display panel LCP. Alternatively, the lightmay not have been concentrated in a viewer direction with respect to asurface of the liquid crystal display panel LCP. Accordingly, for thelight to be entirely used as backlight, it is necessary to concentrateand diffuse the light.

For such a function, the optical film OPT is disposed between the lightguide plate LG and the liquid crystal display panel LCP. The structureof the optical films OPT according to the related art is described belowwith reference to FIGS. 3 to 6. FIG. 3 is a cross-sectional view showingthe structure of optical films including a diffusion film in a liquidcrystal display according to the related art.

The optical films OPT disposed under the liquid crystal display panelLCP of FIG. 3 have a stacked structure, which is widely used. Forexample, the optical films OPT may have a structure in which a lowerprism sheet PRL, an upper prism sheet PRU, and a diffusion sheet DIFhave been sequentially stacked.

Trigonal prism patterns are disposed in parallel on the top surface ofthe lower prism sheet PRL. More specifically, a concave peak portion anda convex valley portion are alternately disposed on the lower prismsheet PRL. Pointed peak portions are arranged in parallel in a firstdirection. The upper prism sheet PRU may also have the same prismpattern as the lower prism sheet PRL. In this case, the tops of theupper prism sheet PRU are disposed in parallel in a second directionorthogonal to the first direction. Light emitted from the light guideplate LG is concentrated in the form of a Gaussian distribution withrespect to a normal line for the surface of the liquid crystal displaypanel LCP, while passing through the lower prism sheet PRL and the upperprism sheet PRU.

The diffusion sheet DIF functions to distribute pieces of light passingthrough the prism sheets PRL and RPU so that the pieces of light have auniform brightness distribution over the entire surface of the liquidcrystal display panel LCP. For example, in the case of the edge-typebacklight unit, a side face in which the light source is positioned mayhave brighter brightness than a side face opposite the side face inwhich the light source is positioned. Furthermore, in the case of thedirect-type backlight unit, a portion in which the light source ispositioned may have a brighter brightness than the surrounding portionof the light source. The diffusion sheet DIF functions to uniformlydiffuse a brightness distribution of light that is not uniform withrespect to the entire surface of the liquid crystal display panel LCP.For such a diffusion function, beads BD may have been distributed to thetop surface of the diffusion sheet DIF.

Light becomes suitable for being used as backlight by the prism sheetsPRL and RPU and the diffusion sheet DIF, but there may be a problem inthat brightness is deteriorated while the light passes through theoptical films. This becomes a cause for deteriorating energy efficiencyrequired to generate backlight. More specifically, brightness issignificantly reduced due to the diffusion sheet DIF. In order to solvesuch a problem, there has been proposed a high brightness diffusion filmDBEF. FIG. 4 is a cross-sectional view showing the structure of opticalfilms including a high brightness diffusion film DBEF in a liquidcrystal display according to the related art.

The high brightness diffusion film DBEF has a high refraction layer anda low refraction layer stacked thereon, and thus solves a problem inthat brightness is reduced by reflecting light lost by reflection to itstop surface again. FIG. 4 has the same structure as FIG. 3 except thatthe high brightness diffusion film DBEF has been disposed in lieu of thediffusion film DIF.

As described above, the optical films according to the related art havea structure in which they have been sequentially stacked between theliquid crystal display panel LCP and the light guide plate LG. That is,the upper prism sheet PRU is disposed on the lower prism sheet PRL inthe lay-down state. Accordingly, a specific air layer is present betweenthe upper prism sheet PRU and the lower prism sheet PRL. The air layerhas a refractive index different from that of the prism sheets PRL andRPU, and thus an effect that pieces of light passing through the prismsheets PRL and RPU are diffused can be obtained.

Likewise, the diffusion film DIF or the high brightness diffusion filmDBEF are also disposed on the upper prism sheet PRU in the lay-downstate. Accordingly, an air layer is present between the upper prismsheet PRU and the diffusion film DIF or between the upper prism sheetPRU and the high brightness diffusion film DBEF. Thus, an effect can beobtained in that pieces of light are diffused while passing through theair layers.

However, a thickness is increased due to the structure in which theoptical films OPT are simply stacked, which becomes an obstacle to thethinness of a liquid crystal display. An attempt is made to make theoptical films OPT ultra-thin by laminating them. If the optical filmsOPT are simply laminated, a brightness distribution is not uniformbecause an air layer disappears and a diffusion effect according to theair layer cannot be obtained. Furthermore, a Moiré pattern, a rainbowMura pattern or a pattern of a hot-spot form is generated. Furthermore,picture quality is deteriorated because moisture according to acapillary phenomenon permeates between the peaks of a prism sheet. Suchirregular brightness, pattern generation, and moisture penetration areevaluated as being a level in which light cannot be suitably used asbacklight, preventing a liquid crystal display from becoming ultra-thin.

SUMMARY

Accordingly, the present invention is directed to a liquid crystaldisplay and a method of manufacturing the same that substantiallyobviate one or more of the problems due to limitations and disadvantagesof the related art.

An object of the present invention is to provide an ultra-thin liquidcrystal display with which an optical film has been integrated.

Another object of the present invention is to provide an ultra-thinliquid crystal display in which a stitch portion is formed between aprism sheet and a support sheet, thus being capable of improvingreliability by preventing the penetration of moisture according to acapillary phenomenon.

Another object of the present invention is to provide an ultra-thinliquid crystal display with which an optical film has been integrated bylaminating a lower polarizer and a prism sheet.

Another object of the present invention is to provide an ultra-thinliquid crystal display capable of preventing the deterioration ofpicture quality in a structure in which a liquid crystal display paneland an optical film have been laminated.

Additional features and advantages of the invention will be set forth inthe description that follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a liquidcrystal display, comprises a display panel; and an optical film on abottom surface of the display panel, the optical film including apolarizer; a support sheet on a bottom surface of the polarizer; and aprism sheet on a bottom surface of the support sheet, the prism sheethaving a base sheet, a prism portion, and a stitch portion over the basesheet, wherein the prism portion includes a plurality of peaks and has aspace defined by a direct contact between the plurality of peaks of theprism portion and the bottom surface of the support sheet.

In another aspect, a method for manufacturing a liquid crystal displaycomprises mounting a source polarizer to which a support sheet isadhered and a first base sheet roll on respective rollers; forming afirst prism sheet roll by inputting resin to a first soft mold andforming a first prism portion comprising a plurality of peaks and afirst stitch portion on the first base sheet roll; fabricating anoptical film comprising a space defined by a direct contact between abottom surface of the support sheet and the plurality of peaks of thefirst prism portion through coalescence of the polarizer roll and thefirst prism sheet roll by a compression roller and cutting of theoptical film; and attaching the optical film to a bottom surface of aliquid crystal display panel.

In another aspect, an optical film comprises a polarizer; a supportsheet on a bottom surface of the polarizer; and a prism sheet on abottom surface of the support sheet, the prism sheet including a basesheet, a prism portion, and a stitch portion formed over the base sheet,wherein the prism portion has a plurality of peaks and has a spacedefined by a direct contact between the plurality of peaks of the prismportion and the bottom surface of the support sheet.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is an exploded perspective view showing the structure of a liquidcrystal display including an edge-type backlight unit according to atechnology of the related art.

FIG. 2 is a cross-sectional view showing the structure of the liquidcrystal display including an edge-type backlight unit according to therelated art taken along line I-I′ of FIG. 1.

FIG. 3 is a cross-sectional view showing the structure of optical filmsincluding a diffusion film in a liquid crystal display according to therelated art.

FIG. 4 is a cross-sectional view showing the structure of optical filmsincluding a high brightness diffusion film in a liquid crystal displayaccording to the related art.

FIG. 5 is a cross-sectional view showing the structure of a liquidcrystal display in which a prism sheet is laminated with a lowerpolarizer according to a first example embodiment of the presentdisclosure.

FIG. 6 is a diagram showing a process for manufacturing a prism sheet.

FIG. 7 is a diagram showing an optical film in which a polarizer and aprism sheet have been laminated.

FIG. 8 is a perspective view showing a structure in which a prism sheetand a lower polarizer have been laminated according to a firstembodiment of the present disclosure.

FIG. 9 is a perspective view showing a prism sheet according to thefirst example embodiment of the present disclosure.

FIG. 10 is a perspective view showing another structure in which a prismsheet and a lower polarizer have been laminated according to the firstexample embodiment of the present disclosure.

FIG. 11 is a perspective view showing a prism sheet according to thefirst example embodiment of the present disclosure.

FIG. 12 is a diagram showing the manufacturing of a prism sheet and aprocess for laminating a prism sheet and a polarizer according to thefirst example embodiment of the present disclosure.

FIGS. 13 and 14 are diagrams showing a prism sheet fabricated accordingto the structure of a soft mold.

FIG. 15 is a cross-sectional view showing a liquid crystal displayaccording to a second example embodiment of the present disclosure.

FIG. 16 is a cross-sectional view showing a liquid crystal displayaccording to a third example embodiment of the present disclosure.

FIG. 17 is a table showing the results of water immersion tests of anoptical film according to the comparative example 1 and embodiments 1and 2 of the present disclosure.

FIG. 18 shows an image of a water immersion test.

FIG. 19 is a table showing the results of high-temperature/high humidityevaluation of a liquid crystal display according to the comparativeexample 2 and embodiments 3 and 4 of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. In thespecification, the same reference numerals denote the same elements. Inthe following description, a detailed description of the known functionsand constitutions will be omitted if it is deemed to make the gist ofthe present disclosure unnecessarily vague. Furthermore, the names ofelements used in the following description have been selected by takinginto consideration only the ease of writing this specification and maybe different from the names of actual parts

First Embodiment

The first example embodiment of the present disclosure is describedbelow with reference to FIGS. 5 to 11. FIG. 5 is a cross-sectional viewshowing the structure of a liquid crystal display in which a prism sheetis laminated with a lower polarizer according to a first exampleembodiment of the present disclosure. FIG. 6 is a diagram showing aprocess for manufacturing a prism sheet. FIG. 7 is a diagram showing anoptical film in which a polarizer and a prism sheet have been laminated.FIG. 8 is a perspective view showing a structure in which a prism sheetand a lower polarizer have been laminated according to a firstembodiment of the present disclosure. FIG. 9 is a perspective viewshowing a prism sheet according to the first example embodiment of thepresent disclosure. FIG. 10 is a perspective view showing anotherstructure in which a prism sheet and a lower polarizer have beenlaminated according to the first example embodiment of the presentdisclosure. FIG. 11 is a perspective view showing a prism sheetaccording to the first example embodiment of the present disclosure.

As shown in FIG. 5, the liquid crystal display (hereinafter referred toas an “LCD”) according to the first example embodiment of the presentdisclosure includes an LCD panel LCP, an upper polarizer UPOL, a lowerpolarizer LPOL, a support sheet SSP, and a prism sheet PS. The LCD panelLCP includes an upper substrate and a lower substrate havingsurface-coalesced with a liquid crystal layer interposed therebetween.The upper polarizer UPOL has coalesced on the top surface of the LCDpanel LCP. The lower polarizer LPOL has coalesced on the bottom surfaceof the LCD panel LCP.

The upper polarizer UPOL has light transmission axes or light blockingaxes aligned in a first direction. The lower polarizer LPOL has lighttransmission axes or light blocking axes aligned in a second direction.If an LCD is normally black, a first light transmission axis and asecond light transmission axis may be disposed to be orthogonal to eachother. In contrast, if an LCD is normally white, the first lighttransmission axis and the second light transmission axis may be disposedin parallel.

The lower polarizer LPOL, although not shown, includes a core layer,that is, a polarizer, and an upper protection layer and lower protectionlayer that have coalesced on the top and bottom surface of the corelayer, respectively. The polarizer is likely to be deformed due tomoisture included in the air. Accordingly, the upper protection layerand the lower protection layer have coalesced on both surfaces of thepolarizer. Furthermore, a protection layer may be formed on at least oneof the top and bottom surfaces of the core layer of the lower polarizerLPOL. The protection layer positioned on the top surface of the corelayer may be an acrylic protection layer and the protection layerpositioned on the bottom surface of the core layer may be TAC, but isnot limited thereto. The lower polarizer LPOL is attached to the LCDpanel LCP through an adhesive layer.

The support sheet SSP is positioned on the bottom surface of the lowerpolarizer LPOL. The support sheet SSP functions to transmit lightincident from a light source and to adhere to the prism sheet PS. Tothis end, the support sheet SSP may be made of a material that cantransmit light incident from the light source and has a great resistanceforce against moisture in the air, for example, any one selected fromthe group consisting of polyethylene terephthalate (PET), polycarbonate(PC), polypropylene (PP), polyethylene (PE), polystyrene (PS), andpolyepoxy (PE), but is not limited thereto. The support sheet SSP may beformed to have a thin thickness in accordance with the thinness of abacklight unit, for example, a thin thickness of 10 μm to 250 μm. If thesupport sheet SSP is formed to have a thickness of 10 μm or more, thebacklight unit can be made as thin as desired within the limit that themechanical physical and heat-resistant properties of an optical film arenot deteriorated. Furthermore, if the support sheet SSP is formed tohave a thickness of 250 μm or less, the thinness of the backlight unitcan be achieved and the mechanical physical and heat-resistantproperties of the optical film can be maximized.

The prism sheet PS is positioned on the bottom surface of the supportsheet SSP. The prism sheet PS includes a prism portion PP having prismpatterns formed on a base sheet SS. The base sheet SS functions totransmit light incident from the light source and to protect the prismportion PP of the prism sheet PS. To this end, the base sheet SS may bemade of a material that can transmit light incident from the lightsource and has a resistance force against moisture in the air, forexample, any one selected from the group consisting of polyethyleneterephthalate (PET), polycarbonate (PC), polypropylene (PP),polyethylene (PE), polystyrene (PS), and polyepoxy (PE), but is notlimited thereto. The base sheet SS may be formed to have a thinthickness in accordance with the thinness of a backlight unit, forexample, a thickness of 10 μm to 250 μm. If the base sheet SS is formedto have a thickness of 10 μm or more, the backlight unit can be made asthin as possible within the limit that the mechanical physical andheat-resistant properties of an optical film are not deteriorated.Furthermore, if the base sheet SS is formed to have a thickness of 250μm or less, the thinness of the backlight unit can be achieved and themechanical physical and heat-resistant properties of the optical filmcan also be maximized.

The prism portion PP is positioned on the base sheet SS, and canconcentrate light incident from the light source by the prism patterns.The prism portion PP may be made of transparent polymer resin totransmit light incident from the light source. In this case, the polymerresin may be made of any one selected from the group consisting ofpolyethylene terephthalate (PET), polycarbonate (PC), polypropylene(PP), polyethylene (PE), polystyrene (PS), and polyepoxy (PE), but isnot limited thereto.

With reference to FIG. 6, the prism sheet PS is formed by coating resinson the base sheet and then imprinting the base sheet using a hard moldHM on a surface of which an inverse image of a prism has been formed.The peaks of the prism are continuously formed in the prism sheet PSformed by the hard mold HM. The prism sheet PS is cut in a desired sizeand used.

As illustrated in FIG. 7, the fabricated prism sheet PS is attached tothe support sheet SSP through adhesives, such as a UV resin, and is thenlaminated with the lower polarizer LPOL, thereby being fabricated intoan integrated optical film OPT. However, the prism sheet PS of theoptical film OPT may experience a capillary phenomenon in which moisturepermeates into the space between the peaks of the prism sheet PS becausethe space between the peaks is exposed to an external environment havingmoisture. If the capillary phenomenon is generated, and the optical filmOPT into which moisture has permeated is applied to the LCD, a fatalproblem, such as deterioration picture quality, may result.

Accordingly, the prism sheet PS according to an embodiment of thepresent disclosure further includes a stitch portion STP formed on thebase sheet SS, as shown in FIG. 5. The stitch portion STP is positionedat least at both edges of the prism sheet PS, and prevents the valley Vbetween a peak P and another peak P of the prism portion PP from beingexposed to the outside.

For example, with reference to FIGS. 8 and 9, the stitch portion STP ispositioned in the direction vertical to the length direction of thepeaks P of the prism portion PP, and fills the entrance of the valleys Vbetween a peak P and another peak P of the prism portion PP. When thesupport sheet SSP is laminated on the prism sheet PS, a path along whichexternal moisture may permeate between a peak P and another peak P ofthe prism portion PP is completely blocked. For example, the peaks P ofthe prism portion PP are attached to the support sheet SSP on both sidesparallel to the length direction of the prism portion PP, therebyblocking the path along which moisture permeates. The stitch portion STPis attached to the support sheet SPS on both sides vertical to thelength direction of the prism portion PP, thereby blocking the pathalong which moisture permeates. Accordingly, external moisture can beprevented from permeating through the valley V between a peak P andanother peak P due to a capillary phenomenon because the stitch portionSTP is formed in the direction vertical to the length direction of theprism portion PP of the prism sheet PS to fill the valley V between apeak P and another peak P of the prism portion PP.

The stitch portion STP includes a length L1 vertical to the lengthdirection of the peaks P of the prism portion PP and a width W1 in thelength direction of the peaks P of the prism portion PP. The length L1of the stitch portion STP has the same length as the prism sheet PS sothat all of the valleys V of the prism portion PP that are exposed tothe outside are filled. The stitch portion STP has a width W1 of atleast 1 mm or more to prevent external moisture from permeating into theinside through the stitch portion STP. Display quality of the LCD panelLCP is not deteriorated because the stitch portion STP is positioned atthe bezel area of the LCD. Accordingly, the width W1 of the stitchportion STP may be smaller than the width of the bezel area of the LCDand the width of the bezel area is different by inches of an LCD, butthe present disclosure is not specially limited.

An LCD may have a shape with a longer length and a shorter width.Furthermore, the lower polarizer LPOL, the support sheet SSP, and theprism sheet PS also have a shape in which a length is long and a breadthis short. In this case, in FIG. 8, the “length” refers to an x-axis andthe “breadth” refers to a y-axis. The peaks P of the prism sheet PS mayhave the length direction arranged in parallel to the length directionof the prism sheet PS, and the prism sheet PS of the stitch portion STPmay have their breadth directions arranged in parallel. Accordingly, thestitch portion STP is disposed in accordance with the bezel in thebreadth direction of the LCD.

With reference to FIGS. 10 and 11, in a prism sheet PS according to anexample embodiment of the present disclosure, the length directions ofthe peaks P are arranged in parallel to the breadth/width direction ofthe prism sheet PS. The stitch portion STP may be arranged in parallelto the length direction of the prism sheet PS to fill the valley Vbetween the peak P and another peak P arranged in the breadth direction.In the prism sheet PS according to an embodiment of the presentdisclosure, if the stitch portion STP is positioned in the directionvertical to the length direction of the peaks P of the prism portion PP,it may be positioned in any direction of the LCD panel, but the presentdisclosure is not limited to this arrangement.

Furthermore, the peaks P of the prism portion PP of the prism sheet mayoverlap or may be spaced apart from each other. Furthermore, the peaks Pof the prism portion PP may have a continuous or discontinuous pattern.Furthermore, the peaks P of the prism portion PP may have a constantheight or may vary in the length direction, and the valleys V of theprism portion PP may have a constant depth or may vary in the lengthdirection. Furthermore, a pitch between adjacent peaks P of the prismportion PP may be constant or may vary. However, the present disclosureis not limited thereto, and the prism portion PP having various lengthsand shapes may be formed by known methods.

Furthermore, the LCD may include a backlight unit under the LCD panelLCP with which the optical film OPT has coalesced. The backlight unitmay be the backlight unit shown in FIG. 1. The backlight unit mayinclude the light source LS, the light guide plate LG, and thereflection plate. More specifically, in an example embodiment of thepresent disclosure, the backlight unit may not include a separateoptical film, but instead may include an optical film attached to theLCD panel LCP. In this case, the backlight unit may further include anadditional optical film, such as a diffusion sheet. Accordingly, lightfrom the backlight unit under the LCD panel LCP can be provided to theLCD panel LCP.

A method for manufacturing the prism sheet according to the firstembodiment of the present disclosure is described below.

FIG. 12 is a diagram showing the manufacturing of a prism sheet and aprocess for laminating the prism sheet and a polarizer according to thefirst example embodiment of the present disclosure. FIGS. 13 and 14 arediagrams showing the prism sheet fabricated according to the structureof a soft mold.

In FIG. 12, the base sheet roll SSF of a prism sheet is mounted on afirst roller R1, a source polarizer POLF to which a support sheet hasadhered is mounted on a second roller R2, and resin inputted to a softmold SM is prepared. The prism sheet having to-be-formed prism patternsformed thereon is wound and mounted on the soft mold SM. Although notshown, when the prism sheet is wound on the soft mold SM, the ends ofthe prism sheet are attached, thus forming a stitch adhesion unit inwhich a prism pattern is not formed. The stitch adhesion unit isdescribed in detail later.

Next, the base sheet roll SSF is transferred to the soft mold SM byrotating the first roller R1, and resin is inputted. The base sheet rollSSF is coated with the resin, and the resin is compressed by the softmold SM, thereby forming the prism portion PP and the stitch portion(not shown). When the prism portion PP and the stitch portion (notshown) are formed on the base sheet roll SSF, semi-hardening isperformed at low pressure, thereby fabricating a prism sheet roll PSF.The polarizer roll POLF is transferred to the compression roller LR byrotating the second roller R2. In this case, prior to a compressionroller LR, UV adhesives are coated so that the prism sheet roll PSF andthe polarizer roll POLF are compressed and attached.

Next, the prism sheet roll PSF and the polarizer roll POLF arecompressed by the compression roller LR at the same time and thuslaminated. The laminated optical film is subjected to ultraviolethardening (MH-UV) and wound and received in a third roller R3. Theoptical film fabricated as described above is cut in a required size,attached to the bottom surface of an LCD, and used.

A method for fabricating the stitch portion included in the prism sheetaccording to an embodiment of the present disclosure is described below.As shown in FIG. 13, the soft mold SM includes fourth and fifth rollersR4 and R5. A prism pattern sheet PPS has been wound on the fourth andthe fifth rollers R4 and R5. The prism pattern sheet PPS has an inverseimage of a prism pattern to be formed on the prism sheet. After theprism pattern sheet PPS is wound on the fourth and the fifth rollers R4and R5, a stitch adhesion unit ST adhered to both edges of the prismpattern sheet PPS is formed to fix the wound prism pattern sheet PPS. Aprism pattern is not formed on the stitch adhesion unit ST.

After resin is inputted to the soft mold MS, when the fourth and thefifth rollers R4 and R5 are rotated, the prism pattern sheet PPScompresses the base sheet SS coated with the resin. When the prismpattern of the prism pattern sheet PPS is compressed on the resin, theprism portion PP is formed on the base sheet SS. Furthermore, when thestitch adhesion unit ST of the prism pattern sheet PPS is compressed onthe resin, the stitch portion STP on which a prism pattern is not formedand a flat resin layer is present is formed.

In this case, when the prism pattern sheet PPS is wound on the fourthand fifth rollers R4 and R5 of the soft mold SM, the length direction ofthe peaks P of the prism of the prism pattern sheet PPS may be disposedin parallel to the rotation direction of the fourth and the fifthrollers R4 and R5, and the stitch adhesion unit ST of the prism patternsheet PPS may be disposed in the direction vertical to the rotationdirection of the fourth and the fifth rollers R4 and R5. Accordingly,the length direction of the peaks P of the prism portion PP formed onthe prism sheet PS may become parallel to or identical with the lengthdirection of the peaks P of the prism of the prism pattern sheet PPS,and the direction of the stitch portion STP formed on the prism sheet PSmay become vertical to the length direction of the peaks P of the prism.

In contrast, as illustrated in FIG. 14, when the prism pattern sheet PPSis wound on the fourth and fifth rollers R4 and R5 of the soft mold MS,the length direction of the peaks P of the prism of the prism patternsheet PPS may be disposed in the direction vertical to the rotationdirection of the fourth and the fifth rollers R4 and R5, and the stitchadhesion unit ST of the prism pattern sheet PPS may be disposed inparallel to the rotation direction of the fourth and the fifth rollersR4 and R5. Accordingly, the length direction of the peaks P of the prismportion PP formed on the prism sheet PS may become vertical to thelength direction of the peaks P of the prism of the prism pattern sheetPPS, and the stitch portion STP formed on the prism sheet PS may becomeparallel to or identical with the length direction of the peaks P of theprism.

As described above, the LCD including the prism sheet according to thefirst example embodiment of the present disclosure can prevent externalmoisture from permeating into a valley due to a capillary phenomenonbecause the valley formed between the peaks of the prism sheet is filledwith the stitch portion. Accordingly, reliability can be improvedbecause a display failure of an LCD is prevented from occurring.

Second Embodiment

A LCD according to a second example embodiment of the present disclosurewill be described below with reference to FIG. 15. FIG. 15 is across-sectional view showing an LCD according to the second exampleembodiment of the present disclosure.

With reference to FIG. 15, the LCD may include an LCD panel LCP, anupper polarizer UPOL, a lower polarizer LPOL, a support sheet SSP, adiffusion sheet DIF, and a prism sheet PS. Unlike the LCD according tothe first example embodiment, the LCD may further include the diffusionsheet DIF between the support sheet SSP and the prism sheet PS. Thediffusion sheet DIF functions to distribute pieces of light passingthrough the prism sheet PS so that they have a uniform brightnessdistribution over the entire surface of the LCD panel LCP. For example,in the case of the edge-type backlight unit, a side face in which alight source is positioned may have a brighter brightness than a sideface opposite the side face in which a light source is positioned.Furthermore, in the case of the direct-type backlight unit, a portion inwhich a light source is positioned may have a brighter brightness thanthe surrounding portion of the light source. The diffusion sheet DIFuniformly diffuses a brightness distribution of light that is notuniform over the entire surface of the LCD panel LCP.

More specifically, the diffusion sheet DIF is integrated with the lowerpolarizer LPOL, the support sheet SSP, and the prism sheet PS throughlamination. The diffusion sheet DIF includes a base sheet BS and adiffusion layer DL coated with beads BD formed on the base sheet BS.

The base sheet BS functions to transmit light incident from a lightsource and to support the diffusion sheet DIF. To this end, the basesheet BS may be made of a material that can transmit light incident fromthe light source and that has a resistance force against moisture in theair, for example, any one selected from the group consisting ofpolyethylene terephthalate (PET), polycarbonate (PC), polypropylene(PP), polyethylene (PE), polystyrene (PS), and polyepoxy (PE), but isnot limited thereto. The base sheet BS may be formed to have a thinthickness in accordance with the thinness of a backlight unit, forexample, a thickness of 10 μm to 250 μm. If the base sheet BS is formedto have a thickness of 10 μm or more, the backlight unit can be madethin as much as possible within the limit that the mechanical physicaland heat-resistant properties of the optical film are not deteriorated.Furthermore, if the base sheet BS is formed to have a thickness of 250μm or less, a thin profile backlight unit can be achieved, and themechanical physical and heat-resistant properties of the optical filmcan also be maximized.

The diffusion layer DL coated with the beads BD is formed on the topsurface of the base sheet BS. The diffusion layer DL has the pluralityof beads BD distributed in resin. Resin that is transparent and hasexcellent heat-resistant and mechanical characteristics may be used asthe resin. For example, polyethylene terephthalate (PET), polycarbonate(PC), polycarbonate (PC) alloy, polystyrene (PS), heat-resistantpolystyrene (PS), polymethylmetaacrylate (PMMA), polybutyleneterephtalate (PBT), polypropylene (PP), polyethylene (PE), acrylonitrilebutadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinylchloride (PVC), a stylene acrylonitrile mixture (SAN), ethylene-vinylacetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP),urea (UF), melanin (MF), unsaturated polyesters (UP), silicon (Si), orcycloolefinepolymer may be used as the resin.

The plurality of beads BD may be fabricated using resin that is the samekind as the aforementioned resin or different from the aforementionedresin. 10 to 50 weight % of the plurality of beads BD may be included inthe resin. The size of the bead BD may be properly selected depending onthe thickness of the resin, and may be 1 to 10 μm. The beads BD may havesubstantially the same size, and a distribution of the beads BD may alsobe regular within the resin. Alternatively, the beads BD may havedifferent sizes, and a distribution of the beads BD may be irregularwithin the resin.

Although not shown, a protection layer including a plurality of beadsmay be positioned on the bottom surface of the diffusion sheet DIF, butthe present disclosure is not limited thereto. The prism sheet PS ispositioned under the diffusion sheet DIF. The prism sheet PS has astructure in which a prism portion PP and a stitch portion STP have beenformed in on a base sheet SS, and has the same configuration as theprism sheet PS according to the first example embodiment. The prismsheet PS has been described in detail in connection with the firstembodiment, and a description thereof is omitted.

In the LCD according to the second example embodiment of the presentdisclosure, a lower polarizer roll to which a support sheet roll, adiffusion sheet roll, and a prism sheet roll are laminated at the sametime, and the lower polarizer roll, the support sheet roll, thediffusion sheet roll, and the prism sheet roll are laminated to form anintegrated optical film. The fabricated optical film is cut in arequired size, attached to the bottom surface of the LCD, and used.

Here, the diffusion sheet DIF has been illustrated as being includedbetween the lower polarizer LPOL and the prism sheet PS, but the presentdisclosure is not limited thereto. For example, the diffusion sheet DIFmay be positioned under the prism sheet PS and may be integrated withthe lower polarizer LPOL, the support sheet SSP, and the prism sheet PS.

The LCD according to the second example embodiment may have an advantagein that an integrated optical film can be fabricated by laminating thelower polarizer, the support sheet, the diffusion sheet, and the prismsheet. Furthermore, external moisture can be prevented from permeatingthrough a valley due to a capillary phenomenon by filling the valleyformed between the peaks of the prism sheet with the stitch portion.Accordingly, reliability can be improved because a display failure of anLCD is prevented from occurring.

Third Embodiment

An LCD according to a third example embodiment of the present disclosurewith be described below with reference to FIG. 16. FIG. 16 is across-sectional view showing the LCD according to the third exampleembodiment of the present disclosure.

As illustrated in FIG. 16, the LCD may include an LCD panel LCP, anupper polarizer UPOL, a lower polarizer LPOL, a support sheet SSP, afirst prism sheet PS1, and a second prism sheet PS2. Unlike the LCDsaccording to the first and second example embodiments, the LCD of thethird example embodiment may include the first prism sheet PS1 and thesecond prism sheet PS2 under the support sheet SSP.

The first prism sheet PS1 has a structure in which a first prism portionPP1 having a plurality of prism patterns disposed therein and a firststitch portion STP1 formed to fill the valleys V of the first prismportion PP1 are formed on a first base sheet SS1. Furthermore, thesecond prism sheet PS2 also has a structure in which a second prismportion PP2 having a plurality of prism patterns disposed therein and asecond stitch portion STP2 formed to fill the valleys of the secondprism portion PP2 are formed on a second base sheet SS2. Each of theelements has been described above, and a description thereof is omitted.

In the first prism sheet PS1, the length direction of the peaks P of thefirst prism portion PP1 is disposed in a y-axis direction, and the firststitch portion STP1 is disposed in an x-axis direction. In the secondprism sheet PS2, the length direction of the peaks P of the second prismportion PP2 is disposed in the x-axis direction, and the second stitchportion STP2 is disposed in the y-axis direction. That is, the lengthdirection of the peaks P of the first prism sheet PS1 and the lengthdirection of the first stitch portion STP1 are vertical to the lengthdirection of the peaks P of the second prism sheet PS2 and the lengthdirection of the second stitch portion STP2. Accordingly, light incidentfrom a light source can be concentrated in the form of a Gaussiandistribution with respect to a normal line for a surface of the LCDpanel LCP while passing through the first prism sheet PS1 and the secondprism sheet PS2.

In the LCD, regarding the lower polarizer LPOL, the support sheet SSP,the first prism sheet PS1, and the second prism sheet PS2, after each ofa first prism sheet roll and a second prism sheet roll is formed using asoft mold, the first prism sheet roll and the second prism sheet roll,together with a source lower polarizer to which a source support sheethas adhered, are laminated at the same time. The source lower polarizer,the source support sheet, the first prism sheet roll, and the secondprism sheet roll are laminated to form an integrated optical film. Thefabricated optical film is cut in a desired size, attached to the bottomsurface of an LCD, and used.

In the LCD configured as such, an integrated optical film can befabricated by laminating the lower polarizer, the support sheet, thefirst prism sheet, and the second prism sheet. Furthermore, externalmoisture can be prevented from permeating into a valley due to acapillary phenomenon by filling the valley formed between the peaks ofthe prism sheet with the stitch portion. Accordingly, reliability can beimproved because a display failure of an LCD is prevented.

Experimental data regarding the optical characteristics of LCDsaccording to comparative examples and embodiments of the presentdisclosure are described below. FIG. 17 is a table showing the resultsof water immersion tests of an optical film according to comparativeexample 1 and example embodiments 1 and 2 of the present disclosure.FIG. 18 shows an image of a water immersion test. FIG. 19 is a tableshowing the results of high temperature/high humidity evaluation of aliquid crystal display according to comparative example 2 andembodiments 3 and 4 of the present disclosure. In this case, the LCDaccording to comparative example 2 included an optical film according tocomparative example 1, and the LCD according to the third embodimentincluded the optical film according to the second embodiment.

With reference to FIGS. 17 and 18, a capillary phenomenon was stronglygenerated through a valley of the prism sheet, and thus moisturepermeated into the optical film in comparative example 1. In the opticalfilm according to the first example embodiment, the width of the stitchportion was 0.5 mm. A small amount of moisture permeated into theoptical film due to a capillary phenomenon that was partially generatedthrough a valley of the prism. In contrast, in the optical filmaccording to the second embodiment, the width of the stitch portion was1 mm, a capillary phenomenon was not generated, and thus, moisture didnot permeate into the optical film.

Furthermore, with reference to FIG. 19, as the results of the evaluationof high temperature/high humidity of the LCD according to thecomparative example 2, a capillary phenomenon was generated through avalley of the prism, and thus, moisture permeated into the optical film.In contrast, as the results of high-temperature/high humidity evaluationof the LCD according to the third example embodiment, a capillaryphenomenon was not generated and moisture never permeated into theoptical film.

It can be seen from the results that a capillary phenomenon can beprevented. Thus, the permeation of moisture can be prevented by formingthe stitch portion in the prism sheet to block a path along whichmoisture permeates. For example, the LCD according to the embodiments ofthe present disclosure can prevent the permeation of external moisturethrough a valley due to a capillary phenomenon by filling the valleyformed between the peaks of the prism sheet with the stitch portion.Accordingly, a display failure of an LCD can be prevented fromoccurring, and thus, reliability can be improved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the liquid crystal displayand method for manufacturing the same of the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method for manufacturing a liquid crystaldisplay, comprising: mounting a source polarizer to which a supportsheet is adhered and a first base sheet roll on respective rollers;forming a first prism sheet roll by inputting resin to a first soft moldand forming a first prism portion comprising a plurality of peaks and afirst stitch portion on the first base sheet roll; fabricating anoptical film comprising a space defined by a direct contact between abottom surface of the support sheet and the plurality of peaks of thefirst prism portion through coalescence of the polarizer roll and thefirst prism sheet roll by a compression roller and cutting of theoptical film; and attaching the optical film to a bottom surface of aliquid crystal display panel, and wherein the first stitch portion is ina direction perpendicular to a length direction of the peaks of thefirst prism portion.
 2. The method of claim 1, wherein the first softmold comprises rollers and a prism pattern sheet wound on the rollers,and wherein a prism pattern and a stitch adhesion unit are formed on theprism pattern sheet.
 3. The method of claim 1, further comprising:mounting a diffusion sheet roll on a roller; and fabricating the opticalfilm through coalescence of the diffusion sheet roll along with thepolarizer roll and the first prism sheet roll by a compression rollerand cutting of the optical film.
 4. The method of claim 1, furthercomprising: mounting a second base sheet roll on a roller; forming asecond prism sheet roll by inputting resin to a second soft mold andforming a second prism portion and a second stitch portion on the secondbase sheet roll; and fabricating the optical film through coalescence ofthe second prism sheet roll along with the source polarizer and thefirst prism sheet roll by a compression roller and cutting of theoptical film.
 5. The method of claim 1, wherein the first stitch portionis at least at both sides of the prism sheet.
 6. The method of claim 1,wherein the first stitch portion fills a valley between adjacent peaksof the first prism portion.
 7. The method of claim 1, wherein the firststitch portion has a width of at least 1 mm.
 8. The method of claim 1,further comprising an additional prism sheet under the first prismsheet.
 9. The method of claim 1, wherein the polarizer includes at leastone core layer.
 10. The method of claim 9, wherein the polarizer furthercomprises a protection layer on at least one surface of the core layer.11. The method of claim 1, further comprising a backlight unitconfigured to provide light to the bottom surface of the liquid crystaldisplay panel, the backlight unit including a light source, a lightguide plate, and a reflection plate.